MICRO-ELELCTRO-MECHANICAL SYSTEM DEVICE AND METHOD FOR FABRICATING THE SAME
A method for fabricating a micro-electro-mechanical system (MEMS) device includes following steps. A cap layer is formed on an MEMS structure. The MEMS structure has a plurality of sacrificial structures. The cap layer has a plurality of release holes. The release holes are located on the sacrificial structures. A dielectric layer is formed on the cap layer, and the dielectric layer fills the release holes. A planarization process is performed on the dielectric layer. The sacrificial structures are then removed to form at least one cavity in the MEMS structure.
This application claims the priority benefit of Taiwan application serial no. 103140244, filed on Nov. 20, 2014. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
FIELD OF THE INVENTIONThe invention relates to an electronic device and a method for fabricating the same. More particularly, the invention relates to a micro-electro-mechanical system (MEMS) device and a method for fabricating the same.
DESCRIPTION OF RELATED ARTA micro-electro-mechanical system (MEMS) device is an industrial technique combining micro-electronic technology and mechanical engineering. The MEMS device may include tiny electromechanical devices (e.g., switches, mirror surfaces, capacitors, accelerometers, sensors, capacitance sensors, actuators, and so on), and these electromechanical devices and integrated circuits may be integrated into one chip. However, in general, the MEMS device in the entire package structure is fragile and may be affected and impaired by static electricity or surface tension. Hence, to protect the MEMS device from pollution or damages, the MEMS device is often sealed between the chip and an ex-situ cap.
Nevertheless, using the ex-situ cap to protect the MEMS device may raise packaging difficulties. Besides, even though the ex-situ cap is employed to protect the MEMS device, the yield of the resultant device may not be satisfactory due to the insufficient mechanical strength of the hollow MEMS structure while a planarization process is performed.
SUMMARY OF THE INVENTIONThe invention is directed to a micro-electro-mechanical system (MEMS) device and a method for fabricating the same, whereby a process for manufacturing an ex-situ cap is no longer required, a chip area can be reduced, and manufacturing costs can be lowered down accordingly.
The invention is directed to an MEMS device and a method for fabricating the same, whereby the mechanical strength of the resultant MEMS device is improved, and the manufacturing yield can be improved as well.
The invention is directed to an MEMS device and a method for fabricating the same; the height and the thickness of the resultant MEMS device are both reduced, and therefore the flexibility of the packaging process can be improved.
In an embodiment of the invention, a method for fabricating an MEMS device includes following steps. An MEMS structure is formed on a substrate. The MEMS structure has at least one cavity therein. A first dielectric layer that covers the MEMS structure is formed, and the first dielectric layer fills the at least one cavity. A cap layer is formed on the first dielectric layer. The cap layer has a plurality of release holes located on the MEMS structure. A second dielectric layer is formed on the cap layer. The second dielectric layer fills the release holes. A planarization process is formed on the second dielectric layer to form a planarized second dielectric layer. The first dielectric layer is still located on the MEMS structure and in the at least one cavity. A release process is performed to remove the planarized second dielectric layer above the release holes and the first dielectric layer below the release holes.
According to an embodiment of the invention, before the MEMS structure is formed, the method further includes forming a stop layer on the substrate correspondingly located below the MEMS structure.
According to an embodiment of the invention, the method further includes forming a plurality of support structures in the MEMS structure, and the support structures are respectively connected to the cap layer and a conductive layer below the MEMS structure.
According to an embodiment of the invention, the release process includes an etching process. The etching process includes a vapor phase etching process, a liquid-phase etching process, or a combination thereof
According to an embodiment of the invention, after the release process is performed, the method further includes forming a sealing layer, and the sealing layer covers the MEMS structure.
According to an embodiment of the invention, before the release process is performed, the method further includes forming a conductive pad on the planarized second dielectric layer. The conductive pad is connected to the cap layer.
According to an embodiment of the invention, after the conductive pad is formed, the method further includes forming a passivation layer on the planarized second dielectric layer. The passivation layer covers a portion of the conductive pad. Besides, the passivation layer has an opening that exposes parts of the planarized second dielectric layer on the release holes.
According to an embodiment of the invention, a material of the passivation layer includes silicon nitride (SiN), titanium nitride (TiN), amorphous silicon, or a combination thereof.
According to an embodiment of the invention, the planarization process includes a chemical-mechanical polishing (CMP) process, an etch back process, or a combination thereof.
In an embodiment of the invention, an MEMS device that includes an MEMS structure, a periphery structure, a cap layer, a conductive pad, and a sealing layer is provided. The MEMS structure is located on a substrate. Besides, the MEMS structure has at least one cavity therein. The periphery structure is located on the substrate at one side of the MEMS structure. The cap layer is located on the MEMS structure and the periphery structure. The conductive pad is located on the cap layer in the periphery structure. The conductive pad is electrically connected to the periphery structure through the cap layer. The sealing layer covers the MEMS structure and a portion of the conductive pad.
According to an embodiment of the invention, the MEMS device further includes a plurality of support structures in the MEMS structure. The support structures are respectively connected to the cap layer and a conductive layer below the MEMS structure.
According to an embodiment of the invention, a material of the support structures includes doped polysilicon, undoped polysilicon, single crystalline silicon, or a combination thereof.
According to an embodiment of the invention, the MEMS device further includes a passivation layer that covers a portion of the conductive pad, and the passivation layer is located between the conductive pad and the sealing layer.
According to an embodiment of the invention, a material of the passivation layer includes SiN, TiN, amorphous silicon, or a combination thereof.
According to an embodiment of the invention, a material of the MEMS structure includes doped polysilicon, undoped polysilicon, single-crystalline silicon, or a combination thereof
According to an embodiment of the invention, a material of the cap layer includes doped polysilicon, undoped polysilicon, single-crystalline silicon, or a combination thereof
According to an embodiment of the invention, a material of the sealing layer includes polymer, SiN, silicon oxide (SiO), or a combination thereof
In an embodiment of the invention, another method for fabricating an MEMS device includes following steps. A cap layer and a dielectric layer are sequentially formed on an MEMS structure. The MEMS structure has a plurality of sacrificial structures therein. The cap layer has a plurality of release holes located on the sacrificial structures. A planarization process is performed on the dielectric layer. The sacrificial structures are then removed to form at least one cavity in the MEMS structure.
According to an embodiment of the invention, the method further includes forming a sealing layer on the cap layer. The sealing layer fills the release holes of the cap layer to seal the MEMS structure.
According to an embodiment of the invention, the method further includes forming a plurality of support structures in the MEMS structure.
In view of the above, an in-situ cap layer in the MEMS device described herein allows the process for manufacturing an ex-situ cap to be omitted; thereby, the chip area can be reduced, and the costs can be lowered down accordingly. From another perspective, compared to the ex-situ cap, the in-situ cap layer described herein is conducive to the reduction of the thickness of the resultant MEMS device, such that the flexibility of the packaging process can be enhanced. Moreover, after the planarization process is performed, the MEMS structure is released; as such, the issue of the insufficient mechanical strength of the hollow MEMS structure can be prevented, and the defect of low yield of the resultant device can be remedied.
Several exemplary embodiments accompanied with figures are described in detail below to further describe the invention in details.
With reference to
Thereafter, a dielectric layer 102, a conductive layer 104, and a dielectric layer 106 are sequentially formed on a front surface S1 of the substrate 100. The dielectric layer 106 covers a surface of the conductive layer 104 and a surface of the dielectric layer 102. In the present embodiment, the dielectric layer 102 is located on the substrate 100, and an electronic device having the dielectric layer 102 is less likely to encounter a feed-through issue. A material of the dielectric layer 102 and a material of the dielectric layer 106 are, for instance, silicon oxide (SiO), silicon nitride (SiN), or a combination thereof, and a method of forming the dielectric layers 102 and 106 includes, for instance, a chemical vapor deposition (CVD) method, a thermal oxidation method, and so forth. The conductive layer 104 covers a portion of the surface of the dielectric layer 102 and lies across the first region R1 and the second region R2. A method of forming the conductive layer 104 includes, for instance, forming a conductive material layer on the dielectric layer 102 and patterning the conductive material layer through performing a lithography and etching process. The conductive material layer may be, for example, doped polysilicon, undoped polysilicon, single-crystalline silicon, or a combination thereof, and the conductive material layer may be formed by performing a CVD process, for example.
With reference to
With reference to
With reference to
With reference to
With reference to
A cap layer 208 is formed on the dielectric layer 204. A method of forming the cap layer 208 includes forming a cap material layer (not shown) on the dielectric layer 204. The cap material layer fills the contact openings 206 to form a plurality of contact holes 206a in the dielectric layer 204 in the first region R1. The cap material layer is then patterned to form two openings 50a and 50b as well as a plurality of release holes 210 in the cap layer 208. The openings 50a and 50b are located in the cap layer 208 in the first region R1 and at two sides of the contact holes 206a. That is, the contact holes 206a are located between the openings 50a and 50b. The release holes 210 are located in the cap layer 208 in the second region R2 and expose surfaces of the dielectric layer 204. In the present embodiment, the release holes 210 and the cavities 202c-202f may be partially overlapped. The dielectric material layer filling the cavities 202c-202f may be considered as sacrificial structures which are subsequently removed in the release process of the MEMS structure 200, as shown in
With reference to
With reference to
A passivation layer 216 is then formed on the conductive pad 214 and the planarized dielectric layer 212a. The passivation layer 216 has an opening 70. The opening 70 exposes the planarized dielectric layer 212a on the release holes 210. A method of forming the passivation layer 216 includes forming a passivation material layer on the substrate 100, for instance. A lithography and etching process is then performed to pattern the passivation material layer. The passivation material layer may be a dielectric material or a semiconductor material, e.g., SiN, TiN, amorphous silicon, or a combination thereof, and the passivation material layer may be formed by performing a CVD process, for instance.
As shown in
With reference to
As shown in
The conductive pad 214 and the periphery structure 320 are located on the substrate 100 at one side of the MEMS structure 310. The conductive pad 214 is located on the cap layer 208 in the periphery structure 320. The conductive pad 214 may be electrically connected to the periphery structure 320 through the cap layer 208 and the contact holes 206a. The periphery structure 320 may be electrically connected to the MEMS structure 310 through the contact window 10a, the conductive layer 104, and the contact window 20a. That is, the conductive pad 214 and the periphery structure 320 are electrically connected to the MEMS structure 310. The subsequent packaging process may be performed on the conductive pad 214 which is not covered by the sealing layer 218. In addition, the MEMS device 300 further includes the passivation layer 216 that covers a portion of the conductive pad 214; besides, the passivation layer 216 is located between the sealing layer 218 and the conductive pad 214 and between the sealing layer 218 and the planarized dielectric layer 212a.
With reference to
To sum up, an in-situ cap layer in the MEMS device described herein allows the chip area to be reduced, and the costs can be lowered down accordingly. From another perspective, compared to the ex-situ cap, the in-situ cap layer described herein is conducive to the reduction of the height and the thickness of the resultant MEMS device, such that the flexibility of the packaging process can be enhanced. Moreover, in an embodiment of the invention, after the planarization process and the thinning process are performed, the MEMS structure is released. Prior to the planarization process, the cavities of the MEMS structure provided herein have the dielectric layer therein, and the dielectric layer contributes to the improvement of the mechanical strength of the MEMS structure, so as to resist the pressure resulting from the planarization process and the thinning process as well as prevent damages to the MEMS structure or collapse of the MEMS structure. Accordingly, the yield of the resultant MEMS device can be improved, and the product having the MEMS device can have the enhanced reliability. In another aspect, the MEMS device provided herein further includes a plurality of support structures. The support structures are alternately arranged in the MEMS structure and may further enhance the mechanical strength of the MEMS structure and the cap layer; as a result, while a wafer dicing process and a packaging process are subsequently performed on the MEMS structure, the MEMS structure can be prevented from damages or collapse.
Although the invention has been described with reference to the above embodiments, it will be apparent to one of ordinary skill in the art that modifications to the described embodiments may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims and not by the above detailed descriptions.
Claims
1. A method for fabricating a micro-electro-mechanical system device, the method comprising:
- forming a micro-electro-mechanical system structure on a substrate, the micro-electro-mechanical system structure having at least one cavity therein;
- forming a first dielectric layer covering the micro-electro-mechanical system structure, the first dielectric layer filling the at least one cavity;
- forming a cap layer on the first dielectric layer, the cap layer having a plurality of release holes, wherein the release holes are located on the micro-electro-mechanical system structure;
- forming a second dielectric layer on the cap layer, the second dielectric layer filling the release holes;
- performing a planarization process on the second dielectric layer to form a planarized second dielectric layer, wherein the first dielectric layer is still located on the micro-electro-mechanical system structure and in the at least one cavity; and
- performing a release process to remove the planarized second dielectric layer above the release holes and the first dielectric layer below the release holes.
2. The method according to claim 1, further comprising forming a stop layer on the substrate correspondingly located below the micro-electro-mechanical system structure before the micro-electro-mechanical system structure is formed.
3. The method according to claim 1, further comprising forming a plurality of support structures in the micro-electro-mechanical system structure, the support structures being respectively connected to the cap layer and a conductive layer below the micro-electro-mechanical system structure.
4. The method according to claim 1, wherein the release process comprises an etching process, and the etching process comprises a vapor phase etching process, a liquid-phase etching process, or a combination thereof.
5. The method according to claim 1, further comprising forming a sealing layer after the release process is performed, the sealing layer covering the micro-electro-mechanical system structure.
6. The method according to claim 1, further comprising forming a conductive pad on the planarized second dielectric layer before the release process is performed, the conductive pad being connected to the cap layer.
7. The method according to claim 6, further comprising forming a passivation layer on the planarized second dielectric layer after the conductive pad is formed, the passivation layer covering a portion of the conductive pad and having an opening, the opening exposing parts of the planarized second dielectric layer on the release holes.
8. The method according to claim 7, wherein a material of the passivation layer comprises silicon nitride, titanium nitride, amorphous silicon, or a combination thereof.
9. The method according to claim 1, wherein the planarization process comprises a chemical-mechanical polishing process, an etch back process, or a combination thereof.
10. A micro-electro-mechanical system device comprising:
- a micro-electro-mechanical system structure located on a substrate, the micro-electro-mechanical system structure having at least one cavity therein;
- a periphery structure located on the substrate at one side of the micro-electro-mechanical system structure;
- a cap layer located on the micro-electro-mechanical system structure and the periphery structure;
- a conductive pad located on the cap layer in the periphery structure and electrically connected to the periphery structure through the cap layer; and
- a sealing layer covering the micro-electro-mechanical system structure and a portion of the conductive pad.
11. The micro-electro-mechanical system device according to claim 10, further comprising a plurality of support structures in the micro-electro-mechanical system structure, the support structures being respectively connected to the cap layer and a conductive layer below the micro-electro-mechanical system structure.
12. The micro-electro-mechanical system device according to claim 11, wherein a material of the support structures comprises doped polysilicon, undoped polysilicon, single-crystalline silicon, or a combination thereof.
13. The micro-electro-mechanical system device according to claim 10, further comprising a passivation layer covering a portion of the conductive pad, the passivation layer being located between the conductive pad and the sealing layer.
14. The micro-electro-mechanical system device according to claim 13, wherein a material of the passivation layer comprises silicon nitride, titanium nitride, amorphous silicon, or a combination thereof.
15. The micro-electro-mechanical system device according to claim 10, wherein a material of the micro-electro-mechanical system structure comprises doped polysilicon, undoped polysilicon, single-crystalline silicon, or a combination thereof.
16. The micro-electro-mechanical system device according to claim 10, wherein a material of the cap layer comprises doped polysilicon, undoped polysilicon, single-crystalline silicon, or a combination thereof.
17. The micro-electro-mechanical system device according to claim 10, wherein a material of the sealing layer comprises polymer, silicon nitride, silicon oxide, or a combination thereof.
18. A method for fabricating a micro-electro-mechanical system device, the method comprising:
- sequentially forming a cap layer and a dielectric layer on a micro-electro-mechanical system structure, the micro-electro-mechanical system structure having a plurality of sacrificial structures therein, the cap layer having a plurality of release holes, wherein the release holes are located on the sacrificial structures;
- performing a planarization process on the dielectric layer, wherein the sacrificial structures are located in the micro-electro-mechanical system structure; and
- removing the sacrificial structures to form at least one cavity in the micro-electro-mechanical system structure.
19. The method according to claim 18, further comprising forming a sealing layer on the cap layer, the sealing layer filling the release holes of the cap layer to seal the micro-electro-mechanical system structure.
20. The method according to claim 18, further comprising forming a plurality of support structures in the micro-electro-mechanical system structure.
Type: Application
Filed: Jun 17, 2015
Publication Date: May 26, 2016
Inventors: Yueh-Kang Lee (Hsinchu County), Li-Yeat Chen (Hsinchu County), Yi-Chaio Lan (Hsinchu County)
Application Number: 14/741,471